Field of the Invention
The present invention relates to a control apparatus that controls driving of an image stabilizer, and more particularly to a control apparatus that controls driving of the image stabilizer in a follow shot.
Description of the Related Art
An image blur produced by influence such as a hand shake applied to a camera is corrected by detecting any fluctuation of the camera and by moving an image stabilizing lens and an image sensor (image stabilizer) in accordance with a result of this detection to change an optical axis. The fluctuation of the camera can be detected with a shake sensor and a unit mounted on the camera in principle, the shake sensor being configured to detect an angular acceleration, an angular velocity, and the like, and the unit being configured to electrically or mechanically integrate an output signal from the shake sensor to output an angular displacement. For example, Japanese Patent Laid-open No. (“JP”) 7-218967 discloses a device for accurate image stabilization that drives the image stabilizer configured to shift an image capturing optical axis based on this detection information and detects the position of the image stabilizer for feedback control.
A follow shot (panning) is one of image capturing methods in a camera. This method captures an image while following, with the camera, the motion of a main object moving, for example, in a horizontal direction. A good follow shot image has a still main object in the image whereas its background flows in the moving direction of the main object. At this time, an image is captured with a slow shutter speed in general to express the dynamism of the object. Experience is required to accurately follow the motion of the object with the camera, and a slow shutter speed is likely to cause a shake. Thus, the follow shot is a relatively difficult image capturing technique for beginners. For this reason, JP 2007-139952 proposes a method for assisting a follow shot through an image stabilizer. Specifically, this method detects the moving speed of the main object on an image plane, and uses its difference from the follow shot speed by a photographer to calculate the moving speed of the main object. During an exposure, the method detects the difference between the moving speed of the main object thus calculated and the follow shot speed by the photographer, or a follow shot speed error. The method performs optical decentering to correct this error, allowing the photographer to capture a nice-looking follow shot image.
The invention disclosed in JP 2007-139952 assumes that a main object targeted by the photographer is identical to a main object recognized by the camera. However, where there are a plurality of objects, it is difficult for the camera to determine on which object the photographer is performing a follow shot mainly, and a false recognition is expected. In other cases, the moving speed of the main object may largely change, and the speed of the follow shot may not be accurately detected. In such a case, the follow shot speed error correction in the invention disclosed in JP 2007-139952 adversely causes a shake of the main object targeted by the photographer.